The aim of our study was to look for significant anomalies in the position of the hyoid bone in maxillomandibular dysmorphoses and disorders of the manducatory apparatus.

This was a 13-month prospective study in patients aged at least 18 years presenting with maxillomandibular dysmorphism and/or dysfunction of the manducatory apparatus and with no previous history of orthodontic treatment or of cervico-maxillo-facial surgery. In all patients, we measured on lateral headfilms the position of the hyoid bone relative to the cervical spine, the cranium, the mandible and the maxilla. The different values were compared with those from a control group.

Of the 56 patients (36 women and 20 men), mean age 38 years, 36 (64.2%) displayed dysfunctions of the manducatory apparatus and 20 (35,7%) exhibited maxillomandibular dysmorphia. The hyoid bone was more posterior in female patients. Its position varied downwards and forwards in dysfunctions of the manductory apparatus and in Angle Class III patients. In Class II patients, the hyoid bone was positioned more posteriorly and cranially. There were no significant differences relative to the cranial base.

In dysfunctions of the manducatory apparatus, the variations were related to the straightness of the spine whereas in cases of dysmorphia, the size and position of the mandible were responsible.